1. Field of the Invention
The present invention relates to a guide pad removably attached to a cutting tool for supporting the cutting tool, a cutting tool body to which the guide pad is attached, and the cutting tool having the guide pad attached thereto.
2. Description of the Related Art
As a conventional guide pad, there is one disclosed in Japanese Patent Laid-Open No. 2003-211311. The guide pad disclosed in Japanese Patent Laid-Open No. 2003-211311 is mounted at an outer circumference of a leading end of a drill head mainly used for deep hole cutting, and abuts on a machining hole machined by the drill, thereby supporting the drill itself. The aforementioned guide pad is removably attached to the drill. The guide pad has a plate-like shape of a substantially rectangular external shape and has a mounting hole formed at the center in a longitudinal direction, and two curved surfaces that are formed on both sides of the mounting hole in a longitudinal direction, and abut on the machining hole as guide surfaces, each having a substantially arc-shaped cross-section. The guide pad includes a guide surface part formed of a cemented carbide, and a steel material part to which the guide surface is brazed and which has a mounting hole to the tool body. That is, the guide pad includes the steel and the brazing materials. The guide pad is formed to have an attachment base portion of the steel material with a substantially L-like cross-section for suppressing generation of cracks in the cemented carbide owing to difference in thermal stress upon brazing of the cemented carbide and the steel material.
Further, as a conventional guide pad, there is one disclosed in International Application Publication No. 96/008332. The guide pad disclosed in International Application Publication No. 96/008332 is formed into a plate-like shape with a substantially rectangular external shape, and has wing-shaped protrusions extending from two long sides thereof, respectively. As the guide pad is entirely formed of the cemented carbide material, the wing-shaped protrusions are provided to prevent reduction in a thickness of the wall from the mounting hole to the outer circumferential side surface for securing the strength of the area around the mounting hole.
In a cutting tool with a single cutting edge for drilling a hole, generally, it is preferable to provide a guide pad at two positions: a 180° position around an axis of rotation with respect to the cutting edge; and a 90° position backward in a relative rotating direction of the tool with respect to the cutting edge, when seen from the leading end side of the tool. In other words, it is preferable to provide it at the farthest position from the cutting edge, and at the position that receives a principal component as the largest among three components of cutting force. However, when the tool diameter that defines the machining hole diameter is relatively small, it is sometimes difficult to provide the guide pad at such preferable positions.
A main reason thereof is interference of a cutting insert or a fastening mechanical part for the cutting insert with the guide pad. Therefore, it is preferable to use the guide pad having no interference, specifically having interference as small as possible, with the other components. However, the wall around the mounting hole is required to have sufficient strength for fastening of the guide pad with a clamp screw and the like. As the cross section of the mounting base portion of the guide pad disclosed in Japanese Patent Laid-Open No. 2003-211311 is formed in substantially L-shape, the guide pad is formed larger in width by the substantially L-shaped wall. In other words, as the guide surface is formed of the separate member from the mounting base portion, the guide pad disclosed in Japanese Patent Laid-Open No. 2003-211311 is not suitable for reducing the size and width. The guide pad disclosed in Pamphlet of International Application Publication No. 96/008332 is entirely formed of a cemented carbide, which is suitable for reducing the size and the width. However, the wing-shape protrusions left-right symmetrically protruding from two long sides of the guide pad are likely to be interfered with the other parts.